An electric railway vehicle is driven using a power supplied from an overhead line through a pantograph. By the way, it would appear that, in typical foreign railway systems, an overhead line is not set up over a yard line of a train shed and a pit line for performing maintenance. In this case, when moving an electric vehicle to a pit line over which an overhead line is not set up, a locomotive with a diesel power not requiring an overhead power moves the electric vehicle to the pit line. In this case, each time the necessity to move the electric vehicle to the pit line occurs, the locomotive with diesel power becomes necessary, and therefore there was a problem that the working efficiency is bad.
Accordingly, a method to drive a main motor at low speed using a battery for control power source which is usually provided in an electric vehicle has been proposed. However, since the voltage of the battery for a control power source is lower compared with a voltage which is usually applied to a DC side of a VVVF inverter for driving the motor, a voltage so as to obtain a prescribed speed, that is a rotational frequency of the motor, will be insufficient.
In such a case, as a configuration so as to boost a voltage of the battery for control power source to a voltage required for a VVVF inverter, technology which is provided with a boosting chopper has been proposed.